statistics
posted by badar .
A sample of 400 high school students showed that they spend an average of 70 minutes a day watching television with a standard deviation of 14 minutes. Another sample of 500 college students showed that they spend an average of 55 minutes a day watching television with a standard deviation of 12 minutes.
a. Construct a 99% confidence interval for the difference between the mean times spent watching television by all high school students and all college students.
b. Test at the 2.5% significance level if the mean time spent watching television per day by high school students is higher than the mean time spent watching television by college students.

Z = (mean1  mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√n
If only one SD is provided, you can use just that to determine SEdiff.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.
Respond to this Question
Similar Questions

Statistics
A student group claims that firstyear students at a university must study 2.5 hours (150 minutes) per night during the school week. A skeptic suspects that they study less than that on the average. A class survey finds that the average … 
Statistics
28. A group of statistics students decided to conduct a survey at their university to find the average (mean) amount of time students spend studying per week. Based on a simple random sample, they surveyed 144 students. The statistics … 
statistics
To determine how many hours per week freshmen college students watch television, a random sample of 225 students was selected. It was determined that the students in the sample spent an average of 35 hours watching TV per week. The … 
Statistics
The average amount of time people spend on facebook each day is 71 minutes, with a standard deviation of 4.7 minutes. Are you more likely to select a random person that spends less than 68 minutes per day, or a group of 35 people that … 
Dine
Men spend an average of 29 minutes per day on weekends and holidays exercising and playing sports. They spend an average of 23 minutes per day reading. A random sample of 25 men resulted in a mean of 35 minutes exercising with a standard … 
Statistics
A recent study of US children under 11 years old found that they spend on average 142 minutes a day watching tv. Assuming normal distribution with the standard deviation of 44 minutes, answer the following. A) what percent of children … 
math 120
A recent poll of a random sample of 400 students at a public 4year college showed the average (mean) amount of time spent using email was 49 minutes per day with a standard deviation of 44 minutes. a. find a 95% confidence interval … 
Stat
Suppose that a principal of a local high school tracks the number of minutes his students spend texting on a given school day. He finds that the distribution of minutes spent texting is roughly normal with a mean of 60 and a standard … 
Statistical work
Suppose that a principal of a local high school tracks the number of minutes his students spend texting on a given school day. He finds that the distribution of minutes spent texting is roughly normal with a mean of 60 and a standard … 
Stat
Does anyone know how to solve for this Suppose that a principal of a local high school tracks the number of minutes his students spend texting on a given school day. He finds that the distribution of minutes spent texting is roughly …